Method and apparatus for mixing gases

Abstract: In a method for cooling a process gas with a cooling gas being admixed into the process gas, wherein one or more streams of the cooling gas are injected into one or more streams of the process gas and the streams of the obtained gas mixture being brought into a spiral movement in a cylindrical mixing chamber with a central distribution chamber (4) and being further provided with a number of spiral blades (6) mounted on the distribution chamber and having perforations, so that each stream of the gas mixture periodically is divided into a number of substreams with a radial flow direction through the perforations of the blades towards the distribution chamber and into a number of substreams with a tangential flow directions along the blades towards the distribution chamber, and the substreams are recombined in the distribution chamber.

Description: The present invention relates to mixing of gases being at different conditions. In particular, the invention concerns a static mixer for use in the mixing of gases. Mixing of gases is usually carried out in static mixers. Mixers of that type conventionally comprise cross corrugated guide surfaces or mixer blades with helical or screw threaded form being rigidly mounted in a tubular enclosure. A gas stream is, thereby, mixed with another gas-stream in a turbulent flow in a plurality of substreams being injected into each other at a certain angle or being combined in a swirling flow motion to a homogeneous gas mixture. A drawback of the known methods and mixers of the above type is a large space necessarily used for obtaining turbulent or swirling flow motion. When gases are mixed in a reactor extra space within the expensive pressure shell is necessary for mixing. A static mixer with a short length is disclosed in DE-A-2,438,392. The static mixer of this disclosure comprises within a cylindrical shell a distribution chamber concentrically arranged within the shell and a guide plate fitting the cross-sectional area of an annular mixing chamber between the distribution chamber and the shell. The mixing chamber is provided with a spiral blade mounted on the guide plate and extenting from the distribution chamber to the shell. An incoming gas mixture is thereby distributed from the central distribution chamber and passed outwardly through the spiral blade to the outermost winding of the spiral blade. It has now surprisingly been found that mixing of gases may be carried out within a still narrower space by mixing different gases as a level matrix obtained by dividing the gases continuously in a plurality of substreams directing the substream in different flow directions towards a central collecting or distribution chamber. Accordingly, this invention provides a static mixer for use in the mixing of different gas streams, comprising within a cylindrical shell, a ring jet arranged at periphery of the mixer, a collection chamber concentrically arranged within the shell, a horizontal guide plade fitting the cross-sectional area of an annular mixing chamber between the collection chamber and the shell, the mixing chamber being provided with a number of spiral blades mounted on the guide plate and extending from the collection chamber to the shell, the spiral blades are adapted to divide an incoming gas mixture into a plurality of substreams with a radial direction through perforations in the blades and with a tangential direction along the blades towards the collection chamber. The invention is in particular useful in the cooling of a process gas with a cooling gas being admixed into the process gas. The above objects and features of the invention will become more apparent from the following detailed description with reference to the drawings, in which the sole Figure shows a static mixer according to a specific embodiment of the invention. In the Figure, static mixer 1 consists of a distribution chamber concentrically arranged within cylindrical shell 2. An annular space between chamber 4 and shell 2 is divided in a number of mixing chambers 16 being confined within spiral blades 6 and guide plate 8. When employed in the cooling of a process gas in a catalytic reactor, the mixer will usually be arranged between two catalyst beds, wherein catalyst particles of a top bed rest on a screen (not shown) covering the cross sectional area on top of mixer 1. Hot process gas leaving the catalyst bed enters into mixing chambers 16 and is mixed with a cooling gas being injected into the chambers from a ring jet at the periphery of the mixer. Having entered the mixing chambers, the gases are mixed and homogenized when passing towards distribution chamber 4 in a plurality of substreams with a tangential flow direction (shown by arrow 12) along spiral blade 6 and in a radial flow direction (shown by arrow 14) through openings 10 in spiral blades 6. Thereby, the substreams are remixed whenever a tangential substream meets a radial substream in mixing chambers 16, and a substantial homogeneous gas stream enters into distribution chamber 4. In the above catalytic reactor, homogenized gas will be distributed from chamber 4 to a bottom catalyst bed beneath mixer 1, optionally through a wire mesh gauze at the bottom of the mixer.

Claims: A static mixer for use in the mixing of different gas streams, comprising within a cylindrical shell (2), a ring jet arranged at periphery of the mixer, a collection chamber (4) concentrically arranged within the shell (2), a horizontal guide plate (8) fitting the cross-sectional area of an annular mixing chamber (16) between the collection chamber (4) and the shell (2), the mixing chamber (16) being provided with a number of spiral blades (6) mounted on the guide plate (8) and extending from the collection chamber (4) to the shell (2), the spiral blades (6) are adapted to divide an incoming gas mixture into a plurality of substreams with a radial direction through perforations (10) in the blades (6) and with a tangential direction along the blades (6) towards the collection chamber (4). Use of the static mixer of claim 1 for cooling a process gas with a cooling gas being admixed into the process gas.

Inventors: ALGREEN-USSING SOREN, ALGREEN-USSING , SOREN
Applicants: TOPSOE HALDOR AS, HALDOR TOPSOE A/S
Application year: 1994
Main classification: B01F5
IPC codes: B01J8, B01F5, B01F3